Excel VBA function not working for Class -

i have function suppose call self performing summation. when gets line pops window wanting macro. vba not support or missing something?

sub sumup(byval result double, byval number integer)  sumvalue double numvalue integer  numvalue = number  if (number > 0)      sumvalue = numvalue * 2     numvalue = numvalue - 1     sumup(result = sumvalue, number = numvalue)  else     msgbox numvalue end if  end sub 

1.) technically it's not function because doesn't return value, call sumup(result = sumvalue, number = numvalue) wrong

2.) missing dim statements

-->

sub sumup(byval result double, byval number integer)  debug.print "result=" & result & ", number=" & number  dim sumvalue double dim numvalue integer  numvalue = number  if (number > 0)      sumvalue = numvalue * 2     numvalue = numvalue - 1       sumup sumvalue, numvalue  else     msgbox numvalue end if  end sub 

executing

sub testit() sumup 2, 2 end sub 

delivers following output:

result=2, number=2 result=4, number=1 result=2, number=0